How many letters does the top answer for “a slide of a large mass of dirt and rock down a mountain or cliff” have?

The most common answer is landslide (9 letters).

Crossword clue: a slide of a large mass of dirt and rock down a mountain or cliff

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

landslide 9 letters wn-def

a slide of a large mass of dirt and rock down a mountain or cliff

landslip 8 letters wn-def

a slide of a large mass of dirt and rock down a mountain or cliff